JP2001024433A - Oscillator and voltage controlled oscillator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase C/N by constituting a feedback circuit of only a capacitor and a line for wiring this and oscillating it at a frequency higher than a fixed value so as to reduce the loss of the feedback circuit. SOLUTION: A voltage-controlled oscillator is constituted by the parallel connection of an amplifier circuit 2 and a feedback circuit 11. In the circuit 2, a collector-connected silicon bipolar transistor is used, a base is used as input and an emitter is used as output. As resistance, base bias resistance and emitter bias resistance are arranged. A feedback circuit 11 comprises a capacitor 5, a parallel plate capacitor 10 and a varactor circuit 8. An oscillation frequency band is finely adjusted by trimming the electrode pattern area of the capacitor 10. The voltage control of an oscillation frequency is executed by applying voltage to a control terminal 84. This oscillator generates oscillation by using the oscillation frequency equal to or higher than 2 GHz.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a UHF band or S
The present invention relates to an oscillator and a voltage controlled oscillator used in the HF band.

[0002]

2. Description of the Related Art A conventional technique will be described with reference to the drawings.

FIG. 4 is a circuit diagram of a conventional voltage controlled oscillator. The feedback circuit 1 and the amplifier circuit 2 are connected in parallel. The configuration of the feedback circuit 1 is a π-type circuit including an inductive circuit 3 and capacitors 4 and 5. Inductive circuit 3 is resonator 3
1 and the oscillator is a Colpitts oscillation circuit. The amplifier circuit 2 is a common-collector amplifier circuit.

The operation of the conventional voltage controlled oscillator will be described. The oscillator oscillates at a frequency that satisfies both the phase condition and the amplitude condition. Considering the phase condition, the necessary condition of the feedback circuit 1 is that the signs of the reactances of the capacitors 4 and 5 are the same and have different signs from those of the inductive circuit 3. Therefore, for example, it is possible to oscillate by using an inductor instead of the capacitors 4 and 5 and using a capacitor instead of the inductive circuit 3. An oscillator having such a configuration is called a Hartley oscillator.

Since the conventional voltage-controlled oscillator is a Colpitts oscillator, the sign of the reactance of the inductive circuit 3 needs to be positive. Therefore, the inductive circuit 3 includes the resonator 31
Is included. The fact that the sign of the reactance of the resonator 31 becomes positive when the oscillation frequency is lower than the resonance frequency of the resonator 31 is used. When controlling the frequency by voltage, the capacitance of the varactor diode 32 is changed by the voltage applied to the control terminal 34, and the reactance of the inductive circuit 3 is changed.

The inductor 33 is for biasing the varactor diode and has a sufficiently high impedance at the oscillation frequency as compared with other elements, so that the loss of the high-frequency power is small. To finely adjust the oscillation frequency band, the reactance of the inductive circuit 3 is finely adjusted. In the case of a voltage-controlled oscillator for mobile communication, a strip line resonator is often used as the resonator 31, so that fine adjustment can be performed by adjusting a trimming pattern provided on the line.

A parameter indicating the characteristics of the oscillator is a signal-to-noise ratio (hereinafter referred to as C / N). This is a parameter indicating the ratio between the power of the oscillation signal and the noise power above and below the oscillation spectrum. In UHF and SHF band wireless devices for mobile communication, the magnitude of the C / N of the oscillator affects transmission IM and adjacent channel selectivity. It is extremely important that the feedback circuit 1 has low loss for improving the C / N.

For this reason, in a UHF or SHF band voltage controlled oscillator for mobile communication, a coaxial resonator or a coaxial resonator, instead of an inductor, is used as an inductive component in the inductive circuit 3 in order to secure a desired C / N. Often a stripline resonator is used. In particular, when the application is for a terminal, it is desirable that the device is small and lightweight, and therefore, in most cases, a strip line resonator is provided on a substrate for use. However, the inductor 33 has a high impedance as described above,
Since the high frequency power is blocked, the loss is small. Therefore, it does not necessarily need to be a resonator.

[0009]

As described in the prior art, the resonator used in the voltage controlled oscillator for the terminal is often a strip line resonator. However, stripline resonators have large conductor loss. In general, stripline resonators and inductors have larger conductor loss than capacitors, and thus cause C / N deterioration. In particular, when the oscillation frequency is high, the loss at the line portion increases due to the skin effect, which is a serious problem. Although the loss of the coaxial resonator is small, it is not suitable for terminals because of its large size.

[0010] The oscillator and the voltage controlled oscillator of the present invention include:
It is an object of the present invention to reduce a loss in a feedback circuit and obtain a voltage controlled oscillator having a large C / N.

[0011]

SUMMARY OF THE INVENTION To solve this problem, the present invention relates to an oscillator comprising an amplifier circuit and a feedback circuit, wherein a capacitor is connected to the capacitor without using a resonator in the feedback circuit. Oscillator characterized by oscillating at a frequency of 2 GHz or more by being constituted only by a line that performs
C / N can be improved in the F band.

[0012]

DETAILED DESCRIPTION OF THE INVENTION The invention according to claim 1 of the present invention is an oscillator comprising an amplifier circuit and a feedback circuit, wherein the feedback circuit comprises only a capacitor and a line for wiring the capacitor. Accordingly, the oscillator oscillates at a frequency of 2 GHz or more, and has an effect that the loss of the feedback circuit is reduced because no inductor or stripline resonator is used.

According to a second aspect of the present invention, in the oscillator according to the first aspect, the feedback circuit is a π-type circuit composed of only a capacitor and a line for wiring the capacitor. Since no inductor or stripline resonator is used, the loss of the feedback circuit is reduced, and the oscillation condition is easily satisfied.

According to a third aspect of the present invention, there is provided the oscillator according to the first aspect, wherein the amplifying circuit is constituted by a silicon bipolar transistor. This has the effect of reducing circuit loss and easily satisfying oscillation conditions.

According to a fourth aspect of the present invention, in the oscillator according to the first aspect, the amplifier circuit is constituted by a bipolar transistor whose collector is grounded.
Since an inductor and a stripline resonator are not used, the loss of the feedback circuit is reduced, and the oscillation condition is easily satisfied.

According to a fifth aspect of the present invention, there is provided the oscillator according to the first aspect, wherein the amplifying circuit is constituted by a bipolar transistor whose base is grounded, wherein an inductor or a strip line resonator is used. Therefore, there is an effect that the loss of the feedback circuit is reduced and the oscillation condition is easily satisfied.

According to a sixth aspect of the present invention, a parallel plate capacitor is used for at least one of the capacitors having one end grounded, and the other end forming the parallel plate capacitor is one of the capacitors constituting the feedback circuit. 2. The oscillator according to claim 1, wherein the trimming of the oscillation frequency is enabled by adjusting the area of the pattern provided on the flat plate. Is reduced, and the capacitance of the parallel plate capacitor can be finely adjusted.

According to a seventh aspect of the present invention, trimming of the oscillation frequency is made possible by using a strip line having a gap for at least one capacitor constituting the feedback circuit and adjusting the size of the gap. The oscillator according to claim 1, wherein the inductor and the stripline resonator are not used, so that the loss of the feedback circuit is reduced, and the size of the gap is finely adjusted.
This has the effect of finely adjusting the capacity of the gap.

According to an eighth aspect of the present invention, at least one of the capacitors constituting the feedback circuit of the oscillator according to the first aspect comprises a varactor diode and a bias circuit for the varactor diode. This is a voltage-controlled oscillator, which has an effect that the loss of the feedback circuit is reduced and the oscillation frequency is voltage-controlled because no inductor or stripline resonator is used.

(Embodiment 1) FIG. 1 shows a first embodiment of a voltage controlled oscillator according to the present invention. The amplifier circuit 2 and the feedback circuit 11 are connected in parallel. The amplifier circuit 2 uses a silicon bipolar transistor whose collector is grounded, and its base is an input and its emitter is an output. The resistor 6 is a base bias resistor, and the resistor 7 is an emitter bias resistor. The feedback circuit 11 is a π-type circuit, and includes a capacitor 5, a parallel plate capacitor 10, and a varactor circuit 8. The parallel plate capacitor 10 is configured using the pattern of the circuit board and the ground plane as electrodes. The varactor circuit 8 is constituted by a circuit that operates at high frequency by connecting a varactor diode 82 and a capacitor 81 in series. The inductor 83 and the control terminal 8 are used for biasing the varactor diode 82.
4. A bypass capacitor 85 is used. Feedback circuit 1
1 is equivalently composed of only a capacitance component at a high frequency.

The operation of the voltage controlled oscillator according to the first embodiment of the present invention will be described with reference to FIG. FIG. 2 is a circuit diagram in which only the arrangement of components is changed without changing the electrical structure of FIG. The electrical structure is the same as in FIG. The fact that the first embodiment of the voltage controlled oscillator of the present invention satisfies the oscillation condition at a certain frequency will be described with reference to FIG. The oscillation condition focusing on the impedance when looking at the varactor circuit 8 side from the point A and the impedance when looking at the amplifier circuit 2 side is expressed by the following equation (1).
-1) and (1-2). -Re (Zv)> Re (Za) (1-1) Im (Zv) + Im (Za) = 0 (1-2) where Zv: impedance from the point A to the varactor circuit 8 side Za: amplification from the point A Since the impedance Zv as viewed from the circuit 2 side is the impedance as viewed from the varactor circuit side, it indicates capacitive. Therefore, from the formula (1-2), Za needs to show inducibility. As an example, a parallel plate capacitor 10
The combined capacitance of the capacitor 4 and the capacitor 4 is 0.5 pF,
Is 3 pF, the transistor is 2SC5086, the collector-emitter voltage is 1.2 V, and the collector current is 5 m.
When a small signal simulation was performed as A, a result of Za = −16 + j6.8Ω was obtained at a frequency of 2.3 GHz. Therefore, when the impedance seen from the varactor circuit side is Re (Zv) <16 at a frequency of 2.3 GHz.
If Ω, Im (Zv) = − 6.8Ω, that is, 10 pF, the oscillation condition is satisfied and oscillation occurs.

The fine adjustment of the oscillation frequency band is performed by trimming the electrode pattern area of the parallel plate capacitor 10. Voltage control of the oscillation frequency is performed by a voltage applied to the control terminal 84. A bipolar transistor is used as the transistor 9 with the collector grounded.

Since the feedback circuit 11 does not use an inductor or a resonator, the loss is small, so that a large C / N oscillation can be obtained. Further, since no coaxial resonator is used, a small oscillator and a voltage controlled oscillator can be obtained.

(Embodiment 2) FIG. 3 shows a voltage-controlled oscillator according to a second embodiment of the present invention. Embodiment 1 Except that the transistor 9 is grounded to the base and the parallel plate capacitor 10 is replaced by a strip line 12 having a gap.
Since the configuration is the same as that described above, only the numbers are assigned and the detailed description of the configuration is omitted. The strip line 12 having a gap is a line having a cut or gap in the middle of the line conductor, and has a capacity at both ends of the gap.

Oscillation is possible even when the transistor 9 is grounded at the base. Since the input and output of the grounded base are in phase at the low frequency, the feedback circuit can oscillate by connecting a large-capacity capacitor and a resistor in series. At high frequencies, the input / output phase difference is not zero, but it is not necessary to use an inductor. As an example, a small signal simulation is performed with a combined capacitance of the strip line 12 having a gap and the capacitor 4 of 4 pF, a capacitor 5 of 0.5 pF, a transistor of 2SC5086, a collector-emitter voltage of 1.2 V, and a collector current of 5 mA. When I went, the frequency was 2.3 GH
The result of Za = −38 + j31Ω is obtained at z.
Therefore, when the impedance Zv as viewed from the varactor circuit side is Re (Zv) <38Ω and Im (Z
v) =-31Ω, that is, 2.2 pF, the oscillation condition is satisfied and oscillation occurs. In addition, the capacitance can be as small as 2.2 pF. When a large value is required for the capacitance of the capacitor, the self-resonant frequency of the capacitor may be reduced, and the capacitor may work as an inductor in a used frequency band. Therefore, it can be said that the transistor 9 oscillates more easily when the base is grounded.

[0026]

According to the present invention, an oscillator or a voltage controlled oscillator having a large C / N and a small size can be obtained.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a voltage controlled oscillator according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram in which the arrangement of components is changed without changing the electrical structure of FIG.

FIG. 3 is a circuit diagram of a voltage controlled oscillator according to a second embodiment of the present invention.

FIG. 4 is a circuit diagram of a conventional voltage controlled oscillator.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 feedback circuit 2 amplifier circuit 3 inductive circuit 4, 5 capacitor 6 base bias resistor 7 emitter bias resistor 8 varactor circuit 9 transistor 10 parallel plate capacitor 31 resonator 32 varactor diode 33 inductor 34 control terminal 81 capacitor 82 varactor diode 83 inductor 84 Control terminal 85 Bypass capacitor

 ────────────────────────────────────────────────── ─── Continued from the front page (72) Inventor Hiroshi Higashiya 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture F-term in Matsushita Electric Industrial Co., Ltd. 5J081 AA03 BB07 CC30 DD03 EE03 GG01 JJ14 JJ15 JJ23 KK02 KK09 KK13 KK22 LL01

Claims (8)

[Claims] 1. An oscillator comprising an amplifier circuit and a feedback circuit, wherein the feedback circuit comprises only a capacitor and a line for wiring the capacitor without using a resonator, thereby oscillating at a frequency of 2 GHz or more. An oscillator characterized by: 2. The oscillator according to claim 1, wherein the feedback circuit is a π-type circuit including only a capacitor and a line for wiring the capacitor. 3. The oscillator according to claim 1, wherein the amplifier circuit is constituted by a silicon bipolar transistor. 4. The oscillator according to claim 1, wherein the amplifier circuit is constituted by a bipolar transistor whose collector is grounded. 5. The oscillator according to claim 1, wherein the amplifier circuit is constituted by a bipolar transistor whose base is grounded. 6. A capacitor constituting a feedback circuit,
The use of a parallel plate capacitor as at least one of the capacitors whose one end is grounded, and the trimming of the oscillation frequency is enabled by adjusting the area of a pattern provided on the flat plate at the other end of the parallel plate capacitor. The oscillator according to claim 1, wherein: 7. The oscillation circuit according to claim 1, wherein a strip line having a gap is used for at least one capacitor constituting the feedback circuit, and trimming of the oscillation frequency is enabled by adjusting the size of the gap. Oscillator. 8. A voltage-controlled oscillator according to claim 1, wherein at least one of the capacitors constituting the feedback circuit of the oscillator comprises a varactor diode and a bias circuit for the varactor diode.